Power Management Subsystem; Power Source; Regulator Control; Voltage Regulation - Panasonic GSM EB-A100 Service Manual

5.4. Power Management Subsystem

LCD
Power detection
and latching
NReset
13 MHz
RTC
Circuit
AD6525

5.4.1. Power Source

The battery comprises a single Lithium-Ion (Li-Ion) cell with a nominal voltage of 3.7 V and 780-mAh capacity.
This type of battery has an advantage in weight and size over Nickel Metal Hydride (NiMH) cells.

5.4.2. Regulator Control

The voltage regulators and the reference are enabled based on the status of the battery and input from the user or software.
If the AD6537 is in Deep Discharge Lockout (DDLO) or Under-Voltage Lockout (UVLO) only the Real-Time Clock regulator is
active. If the AD6537 is in Thermal Shutdown only the Real-Time Clock regulator is active.
If the battery is not in Deep Discharge Lockout, Under-Voltage Lockout, or Thermal Shutdown, the Real-Time Clock regulator
and the the reference are always enabled. The other regulators are enabled or disabled based on input from the user or
software. If the user presses the power-on key (KEYON), the regulators required to boot the software are enabled.If a charger is
detected(CHGDET) the regulators required to boot the software are enabled. If the software asserts the DBBON signal the
regulators reguired to maintain the software state are enabled. The VCXOEN signal enables the VCXO regulator.
The analog regulators can be enabled and disabled using CSPORT.

5.4.3. Voltage Regulation

Each power source is specified as follows.
Digital Core LDO (VCORE)
The digital core LDO supplies the baseband circuitry in the handset (baseband processor and baseband converter). The LDO
has been optimized for very low quiescent current at light loads as this LDO is on whenever the handset is switched on.
VMEM
ADP6537
VRTC
SIMVCC
SIM
Circuit
VCORE
VMEM
Figure 5.13. Power management Subsustem Block Diagram
Memory
VBAT
VCORE
VEXT
VMEM
– 5-13 –
Battery
Charging
Circuit